Vulcanized oil and water swellable particulate composite compositions

ABSTRACT

Embodiments herein include a method comprising providing a self-sealing cement slurry comprising an aqueous base fluid, a cementitious material, and a vulcanized oil and water swellable particulate composite, wherein the vulcanized oil and water swellable particulate composite comprises an elastomer, a crosslinked water swellable superabsorbent polymer, and a hydrophobically modified water-soluble polymer; introducing the self-sealing cement slurry into a subterranean formation; and allowing the self-sealing cement slurry to set, wherein the vulcanized oil and water swellable particulate composite is capable of swelling in the presence of a non-aqueous fluid and an aqueous fluid to reduce the permeability of fluid flowpaths in the set self-sealing cement slurry upon loss of structural integrity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/907,500, filed on Jan. 25, 2016, which is the U.S. National Stage ofInternational Application No. PCT/US2013/067398, filed Oct. 30, 2013,the disclosures of which are incorporated herein by reference in theirentireties.

BACKGROUND

The embodiments described herein relate to vulcanized oil and waterswellable particulate composite compositions, which may be used to formself-sealing cement slurries.

Subterranean formation operations (e.g., stimulation operations, sandcontrol operations, completion operations, etc.) often involve placing acement column around a casing (or liner) string in a wellbore. Thecement column is formed by pumping a cement slurry through the bottom ofthe casing and out through an annulus between the outer casing wall andthe formation face of the wellbore, known as primary cementing. Thecement slurry cures in the annular space, thereby forming a column ofhardened cement (or “sheath”) that, inter alia, supports and positionsthe casing in the wellbore and bonds the exterior surface of the casingto the subterranean formation. Among other things, the cement column maykeep fresh water zones from becoming contaminated with produced fluidsfrom within the wellbore. As used herein, the term “fluid” refers toliquid phase fluids and gas phase fluids. The cement column may alsoprevent unstable formations from caving in, thereby reducing the chanceof a stuck drill pipe or a casing collapse. Additionally, the cementcolumn may form a solid barrier to prevent fluid loss or contaminationof production zones. Subsequent secondary cementing operations may alsobe performed.

The degree of success of a wellbore operation involving placement of acement column therefore depends, at least in part, upon the successfulcementing of the wellbore casing. During the completion and/orproductive phase of a wellbore, for example, a cement sheath may besubjected to certain stresses including, among other things, pressureand temperature changes in the wellbore. Additionally, the cement sheathmay shrink and create microannuli between the casing and cement and/orthe formation and the cement sheath. As a result, the cement sheath maydevelop cracks internally or debond from the casing or subterraneanformation itself, resulting in the formation of channels within thecement sheath or at its interfaces within the formation or the casing,thereby creating flow pathways for unwanted fluid invasion andmigration. As used herein, the term “microannulus” and all of itsvariations refers to an inherent quality of cement, where the cementdoes not fully occupy the annulus between the casing and the formationface due to cement shrinkage. As used herein, the term “channel” refersto a defect in the matrix of the set cement, wherein the matrix of theset cement contains one or more cracks which may have sufficientinter-crack connectivity to provide continuous flow paths to enableundesirable fluid flow from the formation or other parts of the wellboreto the wellhead and/or wellbore. Such channels may result in hazardoussituations (e.g., natural gas contamination or accumulation due to lossof zonal isolation).

The formation of channels in a cement sheath may result in loss ofintegrity of the cement sheath and failure of zonal isolation orwellbore structural failure. Because of the damaging effects of fluidinvasion into a cement column, it is desirable to repair cracked orshrunken sheaths as they occur. Traditional techniques may involve, forexample, squeeze cementing. As used herein, the term “squeeze cementing”refers to the process of forcing a cement slurry though channels, holes,or splits in a casing or liner so as to fill the voids and form animpenetrable barrier. Squeeze cementing can be particularly costly andmay also result in a substantial reduction in production efficiency dueto required downtime. Another technique may involve placing a waterswellable compound (e.g., a polymer) into a cement slurry prior topumping the cement slurry into a subterranean formation and forming acement sheath. Traditional water swellable compounds when included incement slurries may absorb water from the slurry during placement andincrease the viscosity of a cement slurry so as to render it unpumpableand/or unsuitable for forming a stable cement sheath. Additionally, suchwater swellable compounds do not swell in the presence of non-aqueousfluids.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of theembodiments, and should not be viewed as exclusive embodiments. Thesubject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to those skilled in the art and having the benefit of thisdisclosure.

FIG. 1 illustrates a system for delivering the self-sealing cementcompositions comprising the vulcanized oil and water swellableparticulate composites to a downhole location.

FIG. 2 illustrates the swellability rate (or % weight gain) of severalvulcanized oil and water swellable particulate composite compositions infresh water at low temperature.

FIG. 3 illustrates the swellability rate (or % weight gain) of severalvulcanized oil and water swellable particulate composite compositions ina brine solution (1% NaCl) at low temperature.

DETAILED DESCRIPTION

The embodiments described herein relate to vulcanized oil and waterswellable particulate composite compositions, which may be used to formself-sealing cement slurries. Specifically, the vulcanized oil and waterswellable particulate composite compositions described herein may form aportion of a cement sheath and may swell in the event of invasion ofnon-aqueous and/or aqueous fluids from the formation or other parts ofthe wellbore, thereby self-sealing any formed channels and flowpathstherein.

Although some embodiments described herein are illustrated by referenceto cementing operations, the vulcanized oil and water swellableparticulate composites disclosed herein may be used in any subterraneanformation operation that may benefit from their swellability in thepresence of either or both of oil and water, for example, as temporaryor permanent barriers to fluid flow during or after a wellbore treatmentoperation. Such treatment operations may include, but are not limitedto, a drilling operation; a stimulation operation; an acidizingoperation; an acid-fracturing operation; a sand control operation; acompletion operation; a scale inhibiting operation; a water-blockingoperation; a clay stabilizer operation; a fracturing operation; afrac-packing operation; a gravel packing operation; a wellborestrengthening operation; a sag control operation; and any combinationthereof.

Moreover, the vulcanized oil and water swellable particulate compositesdescribed herein may be used in any non-subterranean operation that maybenefit from their swellable properties. Such operations may beperformed in any industry including, but not limited to, oil and gas,drilling and completing water wells for drinking supply or irrigation,mining, chemical, pulp and paper, aerospace, medical, automotive, andthe like.

One or more illustrative embodiments disclosed herein are presentedbelow. Not all features of an actual implementation are described orshown in this application for the sake of clarity. It is understood thatin the development of an actual embodiment incorporating the embodimentsdisclosed herein, numerous implementation-specific decisions must bemade to achieve the developer's goals, such as compliance withsystem-related, lithology-related, business-related, government-related,and other constraints, which vary by implementation and from time totime. While a developer's efforts might be complex and time-consuming,such efforts would be, nevertheless, a routine undertaking for those ofordinary skill in the art having benefit of this disclosure.

It should be noted that when “about” is provided herein at the beginningof a numerical list, the term modifies each number of the numericallist. In some numerical listings of ranges, some lower limits listed maybe greater than some upper limits listed. One skilled in the art willrecognize that the selected subset will require the selection of anupper limit in excess of the selected lower limit. Unless otherwiseindicated, all numbers expressing quantities of ingredients, propertiessuch as molecular weight, reaction conditions, and so forth used in thepresent specification and associated claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties sought to be obtained by theexemplary embodiments described herein. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claim, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsand steps. When “comprising” is used in a claim, it is open-ended.

In some embodiments, a method is disclosed comprising providing aself-sealing cement slurry comprising an aqueous base fluid, acementitious material, and a vulcanized oil and water swellableparticulate composite. The vulcanized oil and water swellableparticulate composite comprises a vulcanized elastomer, a crosslinkedwater swellable superabsorbent polymer, and a hydrophobically modifiedwater-soluble polymer. The self-sealing cement slurry is introduced intoa subterranean formation, such as in an annulus formed between a casingstring and the subterranean formation face and allowed to set. If theset self-sealing cement slurry loses its mechanical sealing integritydue to the formation of fluid flowpaths therein or debonding at theinterfaces, the vulcanized oil and water swellable particulate compositeis capable of swelling in the presence of either or both of non-aqueousand aqueous fluids in the fluid exposed flowpaths. The fluid flowpathsmay develop within the set self-sealing cement slurry or at theinterface between the set self-sealing cement slurry and surroundingsurfaces (e.g., the casing string and/or the subterranean formationface). Such fluid flowpaths may form at any time after the self-sealingcement slurry is set, such as during the stimulation, completion, and/orproduction phase of the subterranean formation or any other phase duringthe lifecycle of the wellbore.

In other embodiments, a vulcanized oil and water swellable particulatecomposite is provided that is capable of swelling in the presence ofeither or both of a non-aqueous fluid and an aqueous fluid. Thevulcanized oil and water swellable particulate composite comprises anelastomer, a crosslinked water swellable superabsorbent polymer, and ahydrophobically modified water-soluble polymer. The elastomer comprisesa non-polar monomer, a polar monomer, and an ionizable polar monomer.

The vulcanized oil and water swellable particulate composites disclosedin some embodiments herein may swell in the presence of non-aqueousfluids and/or aqueous fluids. Such non-aqueous fluids may include, butare not limited to, an alkane; an olefin; an aromatic organic compound;a cyclic alkane; a paraffin; a diesel fluid; a mineral oil; adesulfurized hydrogenated kerosene; and any combination thereof.Examples of aqueous fluids that may contact the vulcanized oil and waterswellable particulate composite and cause it to swell may include, butare not limited to, fresh water; saltwater (e.g., water containing oneor more salts dissolved therein); brine (e.g., saturated salt water);seawater; produced water; flowback water; and any combination thereof.Generally, the aqueous fluid may be from any source, provided that itdoes not adversely interfere with the vulcanized oil and water swellableparticulate composites described herein. The non-aqueous and/or aqueousfluids that the vulcanized oil and water swellable particulate compositemay encounter in a wellbore (e.g., in a cement sheath disposed in awellbore) may be from any source including, for example, thesubterranean formation itself (e.g., water zones or hydrocarbonproducing zones) or fluids that are placed downhole for the purpose ofperforming subterranean formation operations.

The elastomer forming a portion of the vulcanized oil and waterswellable particulate composites comprises a non-polar monomer, a polarmonomer, and an ionizable polar monomer. The individual monomers makingup the elastomers described herein may interact so as to impartelasticity, polarit, and bonding ability to inorganic and metal surfacesto the elastomer. The polar monomers may additionally aid in increasingthe hydropilicity of the elastomer, and in some cases, increase thebonding strength between the elastomer and cementitious material,surfaces of a subterranean formation, and/or surfaces of a casingstring.

Suitable non-polar monomers for use in the elastomers disclosed hereinmay include, but are not limited to, a diene (e.g., a butadiene, ahexadiene, a cyclopentadiene, and the like); a substituted diene (e.g.,isoprene); an alpha-olefin (e.g., ethylene, propene, 1-butene,1-pentene, vinyl cyclohexene, styrene, and the like); and anycombination thereof. In some embodiments, the non-polar monomer may bepresent in the elastomer described herein in an amount in the range offrom a lower limit of about 0.1%, 1%, 5%, 10%, 15%, 20%, and 25% to anupper limit of about 50%, 45%, 40%, 35%, 30%, and 25% by total weight ofthe elastomer.

In some embodiments, the polar monomers for use in the elastomersdescribed herein may be non-ionic. Suitable examples of polar monomersfor use in the elastomers described herein may include, but are notlimited to, an acrylonitrile; a N-alkoxyalkyl acrylamide; a vinylacetate; a vinylformamide; a vinyl acetamide; a vinyl methyl ether; avinyl pyrrolidone; an acrylate; a vinyl siloxane; and any combinationthereof. In some embodiments, the polar monomer is capable of generatinga carboxylate group, which may enhance the hydrophilicity of theelastomer and aid in bonding with the cementitious material. Forexample, these polar monomers may permit chemical interaction betweenthem and the cementitious material and/or the metallic or mineralcomponents in the casing or formation, allowing better incorporation ofthe vulcanized oil and water swellable particulate composites within,for example, a self-sealing cement slurry and improve adhesion orbonding within the cement and the cement interfaces. In someembodiments, the polar monomer may be present in the elastomer describedherein in an amount in the range of from a lower limit of about 10%,12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, and 30% to an upper limitof about 50%, 48%, 46%, 44%, 42%, 40%, 38%, 36%, 34%, 32%, and 30% bytotal weight of the elastomer.

Suitable examples of ionizable polar monomers that may be used in theelastomers described herein may include, but are not limited to, acarboxylic acid; a carboxylic acid derivative; a salt of carboxylicacid; a sulfonic acid; a salt of sulfonic acid; and any combinationthereof. The carboxylic acid derivative may be capable of generatingcarboxylic acid or its salt by interaction with the cement matrix. Ingeneral, the carboxylate group or its derivative of the ionizable polarmonomer in the elastomers described herein has the general formula—COOR, wherein R may be a hydrogen; a metal (e.g., an alkali metal, analkaline earth metal, or a transition metal); an ammonium group; aquaternary ammonium group, an acyl group (e.g., acetyl (CH₃C(O)) group);an alkyl group (e.g., an ester); an acid anhydride group; and anycombination thereof. Examples of suitable carboxylate groups mayinclude, but are not limited to carboxylic acid; carboxy esters; carboxyacid anhydrides; monovalent, divalent, and trivalent metal salts ofcarboxy acids; and any combination thereof. In some embodiments, theionizable polar monomers may be present in the elastomer describedherein in an amount in the range of from a lower limit of about 0.1%,0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 2.25%, 2.5%, 2.75%, 3%,3.25%, 3.5%, 3.75%, 4%, 4.25%, 4.5%, 4.75%, and 5% to an upper limit ofabout 10%, 9.75%, 9.5%, 9.25%, 9%, 8.75%, 8.5%, 8.25%, 8%, 7.75%, 7.5%,7.25%, 7%, 6.75%, 6.5%, 6.25%, 6%, 5.75%, 5.5%, 5.25%, and 5% by totalweight of the elastomer.

In some embodiments, the elastomer may be present in the vulcanized oiland water swellable particulate composite in an amount in the range offrom a lower limit of about 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%,48%, 50%, 52%, 54%, and 56% to an upper limit of about 80%, 78%, 76%,74%, 72%, 70%, 68%, 66%, 64%, 62%, 60%, 58%, and 56% by weight of thecombined elastomer, crosslinked water swellable superabsorbent polymer,and hydrophobically modified water-soluble polymer in the vulcanized oiland water swellable particulate composite. Suitable commerciallyavailable elastomers for use in the vulcanized oil and water swellableparticulate composites described herein may include, but are not limitedto KRYNAC® X 146 and KRYNAC® X 750, carboxylated butadiene-acrylonitrileterpolymers, available from LANXESS Deutschland GmbH.

The crosslinked water swellable superabsorbent polymer for use informing the vulcanized oil and water swellable particulate compositesdescribed in some embodiments herein may be capable of absorbing largeamounts of aqueous fluid and retaining such fluid even under relativelyhigh pressures. Suitable crosslinked water swellable superabsorbentpolymers may include, but are not limited to, a crosslinkedpolyacrylate-based polymer (e.g., sodium polyacrylate); a crosslinkedpolyacrylamide-based polymer; a crosslinked polyvinyl alcohol polymer; acrosslinked starch-polyacrylonitrile graft polymer; any copolymerthereof; any terpolymer thereof; and any combination thereof. In someembodiments, the crosslinked water swellable subperabsorbent polymer maybe present in the vulcanized oil and water swellable particulatecomposite in an amount in the range of from a lower limit of about 30%,31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40% to an upper limitof about 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, and 40% byweight of the combined elastomer, crosslinked water swellablesuperabsorbent polymer, and hydrophobically modified water-solublepolymer in the vulcanized oil and water swellable particulate composite.Suitable examples of commercially available crosslinked water swellablesuperabsorbent polymers may include, but are not limited to, HYSORB™8100, a crosslinked polyacrylate homopolymer (sodium salt), availablefrom BASF in Charlotte, N.C. and DIAMOND SEAL™, a crosslinkedpolyacrylamide polymer, available from Halliburton Energy Services, Inc.in Houston, Tex.

The hydrophobically modified water-soluble polymers for use in thevulcanized oil and water swellable particulate composites describedherein may additionally enhance the performance of the vulcanized oiland water swellable particulate composites in aqueous media, such as inthe self-sealing cement slurries described herein or any other aqueousmedia that might benefit from the swellable properties of the vulcanizedoil and water swellable composities. Generally, the hydrophobicallymodified water-soluble polymers are not crosslinked. However, in someembodiments, crosslinking may be permitted. As used herein, the term“hydrophobically modified” refers to a monomer or polymer havinghydrophobic compound(s) chemically attached thereto. The hydrophobicallymodified water-soluble polymer may be cationic; anionic; nonionic; andany combination thereof. In some embodiments, the hydrophobicallymodified water-soluble polymers may have molecular weights in the rangeof from a lower limit of about 500,000, 975,000, 1,450,000, 1,925,000,2,400,000, 2,875,000, 3,350,000, 3,825,000, 4,300,000, and 4,775,000 toan upper limit of about 10,000,000, 9,525,000, 9,050,000, 8,575,000,8,100,000, 7,625,000, 7,150,000, 6,675,000, 6,200,000, 5,725,000,5,250,000, and 4,775,000, and any value therebetween. In someembodiments, the hydrophobically modified water-soluble polymers mayhave molecular weights in the range of from about 1,000,000 to about8,000,000. The hydrophobically modified water-soluble polymers may besynthesized by any method known to those having ordinary skill in theart, such as by a polymerization reaction. In some embodiments, thehydrophobically modified water-soluble polymer is used in the vulcanizedoil and water swellable particulate composites in particulate formduring the production of the vulcanized oil and water swellableparticulate composites.

In some embodiments, the hydrophobically modified water-soluble polymermay be synthesized by hydrophobic modification of a hydrophilic polymer.Suitable hydrophilic polymers may include, but are not limited to, apolyacrylamide; a poly(methacrylamide); a polyvinylamine; a poly(vinylalcohol); a polyvinyl acetate; a polyacrylate; a polyethylene oxide; apolyethylene oxide methyl ether; a polyethylene glycol; a cellulose; achitostan; a polyamide; a polyetheramine; a polyethyleneimine; apolyhydroxyetheramine; a polylysine; a polysulfone; a starch; a gum; aprotein; a poly(itaconic acid); a poly((E)-but-2-enoic acid); apoly(acrylic acid); a poly(malonic acid); a poly(methacrylic acid); apoly(maleic acid); a poly(maleic anhydride); a poly(citraconicanhydride); a poly(2-acrylamidomethylpropanesulfonic acid); apoly(1-allyloxy-2-hydroxypropyl sulfonic acid); a poly(vinylpyrrolidone); a poly(N-vinyl formamide); a poly(diallyldimethylammoniumsulfate); a poly(methacryloylethyltrimethylamine); apoly(dimethylaminopropyl methacrylamide); apoly(2-methacryloxyethyltrimethylammonium chloride); poly(hydroxyethylacrylate); a poly(vinylsulfonic acid); a poly(vinylphosphonic acid); apoly(N-vinyl caprolactam); a poly(N-vinylformamide); a polymer ofN,N-diallylacetamide; a poly(dimethyl-diallyl-ammonium halide); apoly(styrene sulfonic acid); a polymer of methacrylamidoethyltrimethylammonium halide; a poly(N,N-dimethylacrylamide); apoly(dimethylaminoethyl methacrylate); any derivative thereof; anycopolymer thereof; any terpolymer thereof; and any combination thereof.

Specific hydrophilic polymers for use in the hydrophobically modifiedwater-soluble polymers may include, but are not limited to, apoly(dimethyaminoethylmethacrylate); apoly(acrylamide/dimethylaminoethyl methacrylate); a poly(methacrylicacid/dimethylaminoethyl methacrylate); a poly(2-acrylamido-2-methylpropane sulfonic acid/dimentylaminoethyl methacrylate); apoly(acrylamide/dimethylaminopropyl methacrylamide); a poly(acrylicacid/dimethylaminopropyl methacrylamide); a polymer of acrylic acid anda C10-C30 alkyl acrylate; a hydroxyethyl cellulose; any copolymerthereof; any terpolymer thereof; and any combination thereof.

In some embodiments, the hydrophobically modified water-soluble polymersmay be synthesized by a reaction of hydrophilic monomer(s) capable offorming any of the hydrophilic polymers, followed by hydrophobicmodification of the hydrophilic polymer. In other embodiments, thehydrophilically modified water-soluble polymers may be formed by areaction comprising a hydrophilic monomer(s) and a hydrophobicallymodified hydrophilic monomer(s). The hydrophilic monomer(s) for use inany capacity, including as hydrophilic monomer(s) or as hydrophobicallymodified hydrophilic monomer(s), may be any monomer capable of formingany hydrophilic polymer that is capable of hydrophobic modificationeither in its monomer form (as is the case with the hydrophobicallymodified hydrophilic monomer) or after reacting to form a hydrophilicpolymer to become a hydrophobically modified water-soluble polymer.Suitable hydrophilic monomers, for example, for use in any capacitydisclosed herein may be any monomer capable of forming the hydrophilicpolymers described herein. Examples of suitable hydrophilic monomersinclude, but are not limited to, acrylamide; methacrylamide; cellulose;vinylamine; vinyl alcohol; vinyl acetate; alkyl acrylate; an acrylatesalt of alkali earth metal; an acrylate salt of alkaline earth methal;ethylene oxide; ethylene glycol; glucose; glucosamine; ethyleneimine;lysine; a sulfone; acrylic acid; methacrylic acid; an alkali earth metalsalt of methacrylic acid; an alkaline earth metal salt of methacrylicacid; 2-acrylamido-2-methyl propane sulfonic acid; an alkali earth metalsalt of 2-acrylamido-2-methyl propane sulfonic acid; an alkaline earthmetal salt of 2-acrylamido-2-methyl propane sulfonic acid; N,N-dimethylacrylamide; vinyl pyrrolidone; dimethylaminoethyl methacrylate;dimethylaminopropylmethacrylamide; trimethylammoniumethyl methacrylatechloride; hydroxyethyl acrylate; vinyl sulfonic acid; an alkali earthmetal salt of vinyl sulfonic acid; an alkaline earth metal salt of vinylsulfonic acid; vinyl phosphonic acid; an alkali earth metal salt ofvinyl phosphonic acid; an alkaline earth metal salt of vinyl phosphonicacid; vinyl caprolactam; N-vinylformamide; N,N-diallylacetamide;dimethyl-diallyl-ammonium halide; itaconic acid; styrene sulfonic acid;methacrylamidoethyltrimethyl ammonium halide; (E)-but-2-enoic acid;malonic acid; maleic acid; maleic anhydride; citraconic anhydride;1-allyloxy-2-hydroxypropyl sulfonic acid; N-vinyl formamide; diallyldimethylammonium sulfate; methacrylamidopropyltrimethylammoniumchloride; octadecyldimethylammoniumethyl methacrylate bromide;hexadecyldimethylammoniumethyl methacrylate bromide;hexadecyldimethylammoniumpropyl methacrylamide bromide; 2-ethylhexylmethacrylate; hexadecylmethacrylamide; quaternary salt derivatives ofacrylamide; quaternary salt derivatives of acrylic acid; and anycombination thereof.

In some embodiments, the hydrophilic monomers, hydrophilic polymers,and/or the hydrophobically modified hydrophilic monomers mayadditionally be hydrophilically modified so as to, for example,introduce or enhance branching, so long as the function of thehydrophobically modified water-soluble polymer is not adverselyaffected. The hydrophilic modification may occur before or afterhydrophobic modification to a hydrophilic monomer or a hydrophilicpolymer and may be achieved using one or more hydrophilic groups. Anycompound containing hydrophilic groups capable of introducing into orenhancing the hydrophobicity of the polymer or its braches may be usedfor hydrophilic modification. Suitable hydrophilic groups may include,but are not limited to, a hydroxyl group; a carbonyl group; a carboxylgroup; a sulfhydryl group; an amino group; a phosphate group; apolyether group; any derivative thereof; and any combination thereof.Preferably, if a polyether group is used for hydrophilic modification,it also comprises a halogen; sulfonate; sulfate; organic acid;epichlorohydrin-terminated polyethylene oxide methyl ether; or aderivative thereof. Suitable polyether groups include, but are notlimited to, polyethylene oxide; polypropylene oxide; polybutylene oxide;copolymers thereof; terpolymers thereof; and any combination thereof.Typically, the hydrophilic modification of the hydrophilic monomers,hydrophilic polymers, and/or the hydrophobically modified hydrophilicmonomers has a weight ratio in the range of from a lower limit of about1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, and 5:1 to an upperlimit of about 10:1, 9.5:1, 9:1, 8.5:1, 8:1, 7.5:1, 7:1, 6.5:1, 6:1,5.5:1, and 5:1, and any value therebetween.

In some embodiments, the backbone or pendent groups of thehydrophobically modified water-soluble polymer (e.g., the hydrophilicpolymer backbone formed before or after hydrophobic modification withhydrophobic compound(s)) may comprise reactive amino groups capable ofreacting with hydrophobic groups. Suitable amino groups may include, butare not limited to, a dimethyl-amino group, such as those indimethylaminoethyl methacrylate, a dimethylaminopropyl methacrylamide,and any combination thereof. In other embodiments, the hydrophobicallymodified water-soluble polymer backbone may comprise polar heteroatomsincluding, but not limited to, oxygen; nitrogen; sulfur; phosphorous;and any combination thereof in the polymer backbone or pendent groups.Suitable examples may include hydrophobically modified celluloses,starches, gums, and the like. Suitable commercially availablehydrophobically modified water-soluble polymers may include, but are notlimited to METHOCEL™ and ETHOCEL™ available from The Dow ChemicalCompany in Midland, Mich.; ESAFLOR, a hydrophobically modified guaravailable from Lamberti SpA in Gallarate, Varese, Italy; and NATROSOL®PLUS available from Ashland Inc. in Covington, Ky.

The hydrophobic compounds capable of reacting with the hydrophilicpolymer or a hydrophilic monomer to form the hydrophobically modifiedwater-soluble polymers of the embodiments described herein may includean alkyl halide; a sulfonate; a sulfate; an organic acid; any derivativethereof; and any combination thereof. Suitable hydrophobic compoundsinclude, but are not limited to, octenyl succinic acid; an anhydride ofoctenyl succinic acid; an ester of octenyl succinic acid; an imide ofoctenyl succinic acid; an amide of octenyl succinic acid; dodecenylsuccinic acid; an anhydride of dodecenyl succinic acid; an ester ofdodecenyl succinic acid; an imide of dodecenyl succinic acid; an amideof dodecenyl succinic acid; vinyl ester; alkyl ester of acrylic acid;alkylaryl alcohol ester of acrylic acid; alkyl ester of methacrylicacid; alkylaryl alcohol ester of methacrylic acid; alkyl halide;1-vinylnaphthalene; and any combination thereof. In certain embodiments,the hydrophobic compound may have an alkyl chain length of from about 6to about 22 carbons, and any value therebetween. In another embodiment,the hydrophobic group may have an alkyl chain length of from about 7 toabout 20 carbons, and any value therebetween. In still otherembodiments, the hydrophobic compound may have an alkyl chain length offrom about 12 to about 18 carbons, and any value therebetween. In someembodiments, when the hydrophobically modified water-soluble polymercontains polar heteroatoms, particularly oxygen atoms such as incelluloses, the carbon length of the hydrophobic groups may be fromabout 1 carbon to about 20 carbons.

In those embodiments in which the hydrophobically modified water-solublepolymers are formed by first providing a hydrophilic polymer or byproviding a hydrophilic polymer after polymerizing hydrophilic monomers,the molar ratio of hydrophilic polymer or hydrophilic monomers tohydrophobic compound(s) is in the range of from about 99.98:0.02 toabout 90:10, and any value therebetween. In those embodiments in whichthe hydrophobically modified water-soluble polymer is formed by apolymerization reaction of a hydrophilic monomer(s) and ahydrophobically modified hydrophilic monomer(s), the molar ratio of thehydrophilic monomer(s) to hydrophobically modified hydrophilicmonomer(s) in the hydrophobically modified water-soluble polymer is inthe range of from about 99.98:0.02 to about 90:10, and any valuetherebetween.

In some embodiments, the hydrophobically modified water-soluble polymermay be present in the vulcanized oil and water swellable particulatecomposite in an amount in the range of from a lower limit of about 1%,1.25%, 1.5%, 1.75%, 2%, 2.25%, 2.5%, 2.75%, 3%, 3.25%, 3.5%, 3.75%, 4%,4.25%, 4.5%, 4.75%, 5%, 5.25%, and 5.5% to an upper limit of about 10%,9.75%, 9.5%, 9.25%, 9%, 8.75%, 8.5%, 8.25%, 8%, 7.75%, 7.5%, 7.25%, 7%,6.75%, 6.5%, 6.25%, 6%, 5.75%, and 5.5% by weight of the combinedelastomer, crosslinked water swellable superabsorbent polymer, andhydrophobically modified water-soluble polymer in the vulcanized oil andwater swellable particulate composite. Suitable commerciallyhydrophobically modified water-soluble polymers for use in forming thevulcanized oil and water swellable particulate composites described insome embodiments herein may include, but is not limited to, NATROSOL®PLUS CS, Grade 330, a hydrophobically modified hydroxyethyl cellulose,from Ashland Inc., in Covington, Ky.; PEMULEN™ TR-1, a hydrophobicallymodified polyacrylic acid having a relatively low level of hydrophobicgroups, available from The Lubrizol Corporation in Wickliffe, Ohio; andPEMULEN™ TR-2, a hydrophobically modified polyacrylic acid having arelatively high level of hydrophobic groups, available from The LubrizolCorporation in Wickliffe, Ohio.

The vulcanized oil and water swellable particulate composites may besynthesized by any means known to one of skill in the art, provided thatsuch synthesis does not adversely affect the properties of thevulcanized oil and water swellable particulate composites. One suchsynthesis may include mixing the elastomer, the crosslinked waterswellable superabsorbent polymer, and the hydrophobically modifiedwater-soluble polymer together (e.g., in particulate form or as oilemulsions during the manufacturing phase or a separate phase).Thereafter, each component is melt blended together in a process termed“mastication” to form a single component. As used herein, the term “meltblend” refers to melting the elastomer with heat and mechanical mixingenergy at or above the highest glass transition temperature of theelastomer. Thereafter, the melt blended elastomer, the crosslinked waterswellable superabsorbent polymer, and the hydrophobically modifiedwater-soluble polymer may be vulcanized to form the vulcanized oil andwater swellable particulate composites disclosed herein. As used herein,the term “vulcanized” and all of its variants (e.g., “vulcanize” or“vulcanization”) refers to curing the oil and water swellable compositesby treating with sulfur or other radical generators at a hightemperature. Vulcanization may be performed using any suitablevulcanizing agent compatible with the elastomer, the crosslinked waterswellable superabsorbent polymer, and the hydrophobically modifiedwater-soluble polymer. Suitable vulcanizing agents may include, but arenot limited to, organic peroxide, sulfur, sulfur monochloride, sulfurdichloride, morpholine disulfide, alkylphenol disulfide,tetramethylthionium disulfide and selenium dimethyledithiocarbamate; andany combination thereof. In some embodiments, the vulcanizing agent maypreferably be an organic peroxide including, but not limited to,alpha,alpha-Bis(t-butylperoxy)diisopropylbenzene;2,5-dimethyl-2,5-di-(benzoylperoxy)hexane;2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3; di-tert-butyl peroxide;di-tert-butylperoxy-3,3,5-trimethylcyclohexane; tert-butylhydroperoxide; and any combination thereof. A suitable commerciallyavailable vulcanizing agent may include, but is not limited to, VUL-CUP®40KE, an organic peroxide vulcanizing agent present in an inorganicinert support, available from Arkema, Inc. in Colombes, France.

After vulcanization, the vulcanized oil and water swellable particulatecomposites may be ground or otherwise sized by any means to any suitablesize for use in a particular operation. The vulcanized oil and waterswellable particulate composites may be of any shape and size suitablefor use in a particular subterranean formation. In some embodiments, thevulcanized oil and water swellable particulate composites may besubstantially spherical. In such embodiments, the vulcanized oil andwater swellable particulate composites may be sized such that they havean average diameter in the range of from a lower limit of about 20 μm,70 μm, 120 μm, 170 μm, 220 μm, 270 μm, 320 μm, 370 μm, 420 μm, 470 μm,and 520 μm to an upper limit of about 1000 μm, 950 μm, 900 μm, 850 μm,800 μm, 750 μm, 700 μm, 650 μm, 600 μm, 550 μm, and 500 μm. In otherembodiments, the vulcanized oil and water swellable particulatecomposites may be sized such that they have an average diameter of about250 μm to about 750 μm. In still other embodiments, the vulcanized oiland water swellable particulate composites may be preferably sized so asto have an average diameter of about 500 μm. In other embodiments, thevulcanized oil and water swellable particulate composites may besubstantially non-spherical, such as fibrous shaped; polygonal shaped;any other shape; and any combination thereof. In such embodiments, thevulcanized oil and water swellable particulate composites may be sizedsuch that they are capable of passing through mesh, U.S. Sieve Series inthe range of a lower limit of about 625 mesh, 595 mesh, 565 mesh, 535mesh, 505 mesh, 475 mesh, 445 mesh, 415 mesh, 385 mesh, 355 mesh, and325 mesh, to an upper limit of about 18 mesh, 48 mesh, 78 mesh, 108mesh, 138 mesh, 168 mesh, 198 mesh, 228 mesh, 258 mesh, 288 mesh, 318mesh, and 348 mesh.

In some embodiments, the vulcanized oil and water swellable particulatecomposites may be melt blended (or masticated) in the presence of freshwater to facilitate homogenization of the composites. In suchembodiments, the optional fresh water may be present in the range offrom a lower limit of about 5%, 5.25%, 5.5%, 5.75%, 6%, 6.25%, 6.5%,6.75%, 7%, 7.25%, 7.5%, 7.75%, 8%, 8.25%, 8.5%, 8.75%, 9%, 9.25%, and9.5% to an upper limit of about 15%, 14.75%, 14.5%, 14.25%, 14%, 13.75%,13.5%, 13.25%, 13%, 12.75%, 12.5%, 12.25%, 12%, 11.75%, 11.5%, 11.25%,11%, 10.75%, 10.5%, 10.25%, 10%, 9.75%, and 9.5% by weight of thecombined elastomer, crosslinked water swellable superabsorbent polymer,and hydrophobically modified water-soluble polymer in the vulcanized oiland water swellable particulate composite.

In some embodiments, the vulcanized oil and water swellable particulatecomposites may further comprise one selected from the group consistingof a polyvalent metal oxide; a reinforcing agent; a weighting agent; andany combination thereof. The optional polyvalent metal oxides may serveto aid in compounding the components of the vulcanized oil and waterswellable particulate composites described herein and enhance theirswellable properties. Suitable polyvalent metal oxides may include, butare not limited to, magnesium oxide; zinc oxide; and any combinationthereof. Suitable polyvalent metal oxides may include, but are notlimited, to oxides of magnesium, calcium, barium, zinc, aluminum,titanium, zirconium, or bismuth; or bentonite, silica, zeolite, clay,talc, satin white, or smectite. In preferred embodiments, the polyvalentmetal oxide may be magnesium oxide; zinc oxide; and any combinationthereof. In some embodiments, the optional polyvalent metal oxide may bepresent in the range of a lower limit of about 0.01%, 0.1%, 0.2%, 0.3%,0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, and 1% to an upper limit of about2%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, and 1% byweight of the combined elastomer, crosslinked water swellablesuperabsorbent polymer, and hydrophobically modified water-solublepolymer in the vulcanized oil and water swellable particulate composite.

The optional reinforcing agent may serve to increase the hardness of thevulcanized oil and water swellable particulate composites aftervulcanization, as compared to identically formed vulcanized oil andwater swellable particulate composites without the reinforcing agent.Suitable reinforcing agents may include, but are not limited to, carbonblack; silica; and any combination thereof, including carbon blackhaving silica deposited on its surface. In some embodiments, theoptional reinforcing agent may be present in the range of a lower limitof about 0.01%, 0.1%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%,6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%,12.5%, 13%, 13.5%, 14%, 14.5%, and 15% to an upper limit of about 30%,29.5%, 29%, 28.5%, 28%, 27.5%, 27%, 26.5%, 26%, 25.5%, 25%, 24.5%, 24%,23.5%, 23%, 22.5%. 22%, 21.5%, 21%, 20.5%, 20%, 19.5%, 19%, 18.5%, 18%,17.5%, 17%, 16.5%, 16%, 15.5%, and 15% by weight of the combinedelastomer, crosslinked water swellable superabsorbent polymer, andhydrophobically modified water-soluble polymer in the vulcanized oil andwater swellable particulate composite.

The weighting agents may be included in the vulcanized oil and waterswellable particulate composite so as to increase the density of thecomposite such that it is, for example, similar in density to a fluid inwhich it may be suspended. For example, in those embodiments in whichthe vulcanized oil and water swellable particulate composites areincluded in a self-sealing cement slurry comprising the vulcanized oiland water swellable particulate composites, an aqueous base fluid, andcementitious material, the weighting agents may be included such thatthe density of the vulcanized oil and water swellable particulatecomposites are equal to or similar to the self-sealing cement slurry,thus fostering a more homogeneous distribution of the vulcanized oil andwater swellable particulate composites therein. Suitable weightingagents may include, but are not limited to, barium sulfate; potassiumchloride; sodium chloride; sodium bromide; calcium chloride; calciumbromide; ammonium chloride; zinc bromide; zinc formate; zinc oxide; andany combination thereof. In some embodiments, the weighting agent may bepresent in the range of a lower limit of about 0.1%, 0.25%, 0.5%, 0.75%,1%, 1.25%, 1.5%, 1.75%, 2%, 2.25%, 2.5%, 2.75%, 3%, 3.25%, 3.5%, 3.75%,4%, 4.25%, 4.5%, 4.75%, 5%, 5.25%, and 5.5% to an upper limit of about10%, 9.75%, 9.5%, 9.25%, 9%, 8.75%, 8.5%, 8.25%, 8%, 7.75%, 7.5%, 7.25%,7%, 6.75%, 6.5%, 6.25%, 6%, 5.75%, and 5.5% by weight of the combinedelastomer, crosslinked water swellable superabsorbent polymer, andhydrophobically modified water-soluble polymer in the vulcanized oil andwater swellable particulate composite. However, the amount of optionalweighting agent included in the vulcanized oil and water swellableparticulate composites will depend on the weighting agent selected, thefluid into which the vulcanized oil and water swellable particulatecomposite is to be included, and the like.

The vulcanized oil and water swellable particulate composites swell inthe presence of non-aqueous and aqueous fluids. In some embodiments, thevulcanized oil and water swellable particulate composites are capable ofswelling in a range of from about 20% to about 400% by weight in dryform. They are capable of maintaining their form (i.e., they do notseparate or disintegrate into the individual components making up thevulcanized oil and water swellable particulate composites) and thus donot adversely affect the fluids or slurries into which they may beplaced, such as the self-sealing cement slurries disclosed herein.Within the set self-sealing cement sheath, the vulcanized oil and waterswellable particulate composites upon exposure to aqueous or non-aqueousfluid may swell and fill channels or fluid flowpaths of various sizes(i.e., large channels as well as microannuli) formed as a result of lossof integrity to the set self-sealing cement slurries. The vulcanized oiland water swellable particulate composites are also capable ofcompensating for shrinkage of the self-sealing cement slurries duringthe shrinking phase as the cement sets. The vulcanized oil and waterswellable particulate composites may be capable of preventing orreducing shrinkage as the cement sets because of their increasedparticulate volume in the partially or fully swollen state from exposureto fluids in the cement slurry (e.g., water). The self-sealing cementslurries may be placed into a downhole location and at least partiallyset during which phase the degree of cement shrinkage is maximum.Moreover, the presence of the vulcanized oil and water swellableparticulate composites may additionally impart flexibility andresiliency to the self-sealing cement slurries described herein after itis set and during the life of the well, enabling the cement sheath toresist brittle failure under stresses imposed by pressure andtemperature changes. Thus, the mere presence of the vulcanized oil andwater swellable particulate composites may both prevent or reduce theinitial formation of channels and flowpaths, or enhancement thereof, bypreventing or reducing structural integrity losses to the self-sealingcement slurry at the outset, as well as swell to fill any such channelsor flowpaths that are formed due to structural integrity losses.

The self-sealing cement slurries described herein may comprise thevulcanized oil and water swellable particulate composites, which may beincluded in the self-sealing cement slurries after storage in dry formor storage in a high salinity aqueous solution or a non-swellingnon-aqueous solvent (e.g., a hydroxylic solvent such as ethylene glycolor glycerol) to prevent or minimize swelling of the vulcanized oil andwater swellable particulate composites while in storage form. Uponinclusion of the high salinity aqueous solution or the non-swellingnon-aqueous solvent comprising the vulcanized oil and gas swellablecomposites into the self-sealing cement slurry, the high salinityaqueous solution or the non-swelling non-aqueous solvent may besufficiently diluted to allow full swelling of the vulcanized oil andgas swellable composite. In addition, other additives may be included inthe self-sealing cement slurry to reverse any effects of the highsalinity solution that may hinder swelling of the vulcanized oil andwater swellable particulate composites described herein. In otherembodiments, the vulcanized oil and gas swellable composites may beencapsulated (such as with an encapsulating polymer) so as to facilitatestorage or to delay swelling until a particular time or when aparticular condition is met in the subterranean formation (e.g., uponreaching a particular pressure or temperature). In some embodiments, thevulcanized oil and water swellable particulate composites, whether indry form, suspended in a high salinity aqueous solution or thenon-swelling non-aqueous solvent, or encapsulated, may be present in anamount in the range of a lower limit of about 0.1%, 0.25%, 0.5%, 0.75%,1%, 1.25%, 1.5%, 1.75%, 2%, 2.25%, 2.5%, 2.75%, 3%, 3.25%, 3.5%, 3.75%,4%, 4.25%, 4.5%, 4.75%, 5%, 5.25%, 5.5%, 5.75%, 6%, 6.25%, 6.5%, 6.75%,7%, 7.25%, 7.5%, 7.75%, 8%, 8.25%, 8.5%, 8.75%, 9%, 9.25%, 9.5%, 9.75%,and 10% to an upper limit of about 20%, 19.75%, 19.5%, 19.25%, 19%,18.75%, 18.5%, 18.25%, 18%, 17.75%, 17.5%, 17.25%, 17%, 16.75%, 16.5%,16.25%, 16%, 15.75%, 15.5%, 15.25%, 15%, 14.75%, 14.5%, 14.25%, 14%,13.75%, 13.5%, 13.25%, 13%, 12.75%, 12.5%, 12.25%, 12%, 11.75%, 11.5%,11.25%, 11%, 10.75%, 10.5%, 10.25%, and 10% by weight of the combinedaqueous base fluid and cementitious material.

The aqueous base fluid included in the self-sealing cement slurriesdescribed herein may include, but are not limited to, any aqueous basefluid suitable for use in a cement slurry for use in a subterraneanoperation. Suitable aqueous base fluids may include, but are not limitedto freshwater; saltwater (e.g., water containing one or more saltsdissolved therein); brine; seawater; and any combination thereof.Generally, the aqueous base fluid may be from any source, provided, forexample, that it does not contain an excess of compounds that mayundesirably affect the vulcanized oil and water swellable particulatecomposites or the self-sealing cement slurries described herein. In someembodiments, the aqueous base fluid may be included in an amountsufficient to form a pumpable slurry. In some embodiments, the aqueousbase fluid may be included in the self-sealing cement slurries in anamount in the range of a lower limit of about 30% by weight (“w/w”), 40%w/w, 50% w/w, 60% w/w, 70% w/w, 80% w/w, 90% w/w, 100% w/w, 110% w/w,and 120% w/w to an upper limit of about 200% w/w, 190% w/w, 180% w/w,170% w/w, 160% w/w, 150% w/w, 140% w/w, 130% w/w, and 120% w/w by weightof the cementitious material. In some embodiments, the base fluid may beincluded in an amount of about 30% to about 150% w/w of the cementitiousmaterial.

The cementitious material for use in the self-sealing cement slurriesdescribed herein may be any cementitious material suitable for use insubterranean operations. In preferred embodiments, the cementitiousmaterial is a hydraulic cement. Hydraulic cements harden by the processof hydration due to chemical reactions to produce insoluble hydrates(e.g., calcium-silicate hydrate) that occur independent of the cement'swater content (e.g., hydraulic cements can harden even under constantlydamp conditions). Thus, hydraulic cements are preferred because they arecapable of hardening regardless of the water content of a particularsubterranean formation. Suitable hydraulic cements include, but are notlimited to Portland cement; Portland cement blends (e.g., Portlandblast-furnace slag cement and/or expansive cement); non-Portlandhydraulic cement (e.g., super-sulfated cement, calcium aluminate cement,and/or high magnesium-content cement); and any combination thereof. Insome embodiments, the cementitious material may be present in an amountranging from a lower level of at least about 20%, 25%, 30%, 35%, 40%,45%, and 50%, to an upper level of equal to or less than about 80%, 75%,70%, 65%, 60%, 55%, and 50%, wherein each of the percentages are w/w ofthe combined weight of the vulcanized oil and water swellableparticulate composites (including any storage fluid, such as the highsalinity solution discussed above) and the cementitious material. Inpreferred embodiments, the cementitious material may be present in anamount of about 30% to about 60% w/w of the combined weight of thevulcanized oil and water swellable particulate composites (including anystorage fluid, such as the high salinity solution discussed above) andthe cementitious material.

In some embodiments, a portion of the cementitious material may beformed from pozzolanic material, which may aid in increasing the densityand strength of the cementitious material. As used herein the term“pozzolanic material” refers to a siliceous material that is capable ofreacting with calcium hydroxide (which may be produced during hydrationof a cementitious material) in the presence of water to form a materialpossessing the qualities of cementitious material. Because calciumhydroxide accounts for a sizable portion of most hydrated hydrauliccements and because calcium hydroxide does not contribute to thecement's properties, the use of pozzolanic material as a portion of thecementitious material may synergistically enhance the strength andquality of the cement. Any pozzolanic material that is reactive withsome of the hydration products of the cementitious material (e.g.,calcium hydroxide) may be used in the methods and compositions of theembodiments described herein. Suitable pozzolanic materials may include,but are not limited to silica fume; silica flour; metakaolin; fly ash;diatomaceous earth; calcined diatomite; uncalcined diatomite; calcinedfullers earth; pozzolanic clays; calcined volcanic ash; uncalcinedvolcanic ash; bagasse ash; pumice; pumicite; rice hull ash; naturalzeolites; synthetic zeolites; slag; vitreous calcium aluminosilicate;cement kiln dust; lime kiln dust; pumice; and any combination thereof.In some embodiments, the pozzolanic material may be present in an amountranging from a lower level of at least about 1%, 5%, 10%, 15%, 20%, 25%,or 30%, to an upper level of equal to or less than about 40%, 35%, or30%, wherein each of the percentages are w/w of the cementitiousmaterial.

In various embodiments, systems configured for preparing, transporting,and delivering the self-sealing cement slurries comprising thevulcanized oil and water swellable particulate composites describedherein to a downhole location are described. In various embodiments, thesystems can comprise a pump fluidly coupled to a tubular (e.g., acasing, drill pipe, production tubing, coiled tubing, etc.) extendinginto a wellbore penetrating a subterranean formation. The tubular may beconfigured to circulate or otherwise convey the self-sealing cementslurries comprising the vulcanized oil and water swellable particulatecomposites described herein. The pump may be, for example, a highpressure pump or a low pressure pump, which may depend on, inter alia,the viscosity and density of the self-sealing cement slurries, the typeof the cementing operation, and the like.

In some embodiments, the systems described herein may further comprise amixing tank arranged upstream of the pump and in which the self-sealingcement slurries are formulated. In various embodiments, the pump (e.g.,a low pressure pump, a high pressure pump, or a combination thereof) mayconvey the self-sealing cement slurries from the mixing tank or othersource of the self-sealing cement slurries to the tubular. In otherembodiments, however, the self-sealing cement slurries can be formulatedoffsite and transported to a worksite, in which case the self-sealingcement slurries may be introduced to the tubular via the pump directlyfrom a transport vehicle or a shipping container (e.g., a truck, arailcar, a barge, or the like) or from a transport pipeline. In yetother embodiments, the self-sealing cement slurries may be formulated onthe fly at the well site where components of the self-sealing cementslurries are pumped from a transport (e.g., a vehicle or pipeline) andmixed during introduction into the tubular. In any case, theself-sealing cement slurries may be drawn into the pump, elevated to anappropriate pressure, and then introduced into the tubular for deliverydownhole.

FIG. 1 shows an illustrative schematic of a system that can deliverself-sealing cement slurries of the disclosure to a downhole location,according to one or more embodiments. It should be noted that while FIG.1 generally depicts a land-based system, it is to be recognized thatlike systems may be operated in subsea locations as well. As depicted inFIG. 1, system 1 may include mixing tank 10, in which a self-sealingcement slurries of the embodiments described herein may be formulated.Again, in some embodiments, the mixing tank 10 may represent orotherwise be replaced with a transport vehicle or shipping containerconfigured to deliver or otherwise convey the self-sealing cementslurries to the well site. The self-sealing cement slurries may beconveyed via line 12 to wellhead 14, where the self-sealing cementslurries enters tubular 16 (e.g., a casing, drill pipe, productiontubing, coiled tubing, etc.), tubular 16 extending from wellhead 14 intowellbore 22 penetrating subterranean formation 18. Upon being ejectedfrom tubular 16, the self-sealing cement slurries may subsequentlyreturn up the wellbore in the annulus between the tubular 16 and thewellbore 22 as indicated by flow lines 24. In other embodiments, theself-sealing cement slurries may be reverse pumped down through theannulus and up tubular 16 back to the surface, without departing fromthe scope of the disclosure. Pump 20 may be configured to raise thepressure of the self-sealing cement slurries to a desired degree beforeits introduction into tubular 16 (or annulus). It is to be recognizedthat system 1 is merely exemplary in nature and various additionalcomponents may be present that have not necessarily been depicted inFIG. 1 in the interest of clarity. Non-limiting additional componentsthat may be present include, but are not limited to, supply hoppers,pneumatic transport lines, pneumatic cement mixing head, inductionmixing system, valves, condensors, adapters, joints, gauges, sensors,compressors, pressure controllers, pressure sensors, flow ratecontrollers, flow rate sensors, temperature sensors, and the like.

One skilled in the art, with the benefit of this disclosure, shouldrecognize the changes to the system described in FIG. 1 to provide forother cementing operations (e.g., squeeze operations, reverse cementing(where the cement in introduced into an annulus between a tubular andthe wellbore and returns to the wellhead through the tubular), and thelike).

It is also to be recognized that the disclosed self-sealing cementslurries may also directly or indirectly affect the various downholeequipment and tools that may come into contact with the treatment fluidsduring operation. Such equipment and tools may include, but are notlimited to, wellbore casing, wellbore liner, completion string, insertstrings, drill string, coiled tubing, slickline, wireline, drill pipe,drill collars, mud motors, downhole motors and/or pumps, surface-mountedmotors and/or pumps, centralizers, turbolizers, scratchers, floats(e.g., shoes, collars, valves, etc.), wellbore projectiles (e.g.,wipers, plugs, darts, balls, etc.), logging tools and related telemetryequipment, actuators (e.g., electromechanical devices, hydromechanicaldevices, etc.), sliding sleeves, production sleeves, plugs, screens,filters, flow control devices (e.g., inflow control devices, autonomousinflow control devices, outflow control devices, etc.), couplings (e.g.,electro-hydraulic wet connect, dry connect, inductive coupler, etc.),control lines (e.g., electrical, fiber optic, hydraulic, etc.),surveillance lines, drill bits and reamers, sensors or distributedsensors, downhole heat exchangers, valves and corresponding actuationdevices, tool seals, packers, cement plugs, bridge plugs, and otherwellbore isolation devices, or components, and the like. Any of thesecomponents may be included in the systems generally described above anddepicted in FIG. 1.

Embodiments disclosed herein include:

A. A method comprising: providing a self-sealing cement slurrycomprising an aqueous base fluid, a cementitious material, and avulcanized oil and water swellable particulate composite, wherein thevulcanized oil and water swellable particulate composite comprises anelastomer, a crosslinked water swellable superabsorbent polymer, and ahydrophobically modified water-soluble polymer; introducing theself-sealing cement slurry into a subterranean formation; and allowingthe self-sealing cement slurry to set, wherein the vulcanized oil andwater swellable particulate composite is capable of swelling in thepresence of a non-aqueous fluid and an aqueous fluid to reduce thepermeability of fluid flowpaths in the set self-sealing cement slurryupon loss of structural integrity.

B. A vulcanized oil and water swellable particulate compositecomprising: an elastomer, a crosslinked water swellable superabsorbentpolymer, and a hydrophobically modified water-soluble polymer, whereinthe elastomer comprises a non-polar monomer, a polar monomer, and anionizable polar monomer, and wherein the vulcanized oil and waterswellable particulate composite is capable of swelling in the presenceof a non-aqueous fluid and an aqueous fluid.

Each of embodiments A and B may have one or more of the followingadditional elements in any combination:

Element 1: Wherein the elastomer comprises a non-polar monomer, a polarmonomer, and an ionizable polar monomer.

Element 2: Wherein the non-polar monomer is selected from the groupconsisting of a diene; a substituted diene; an alpha-olefin; and anycombination thereof.

Element 3: Wherein the polar monomer is non-ionic.

Element 4: Wherein the polar monomer is selected from the groupconsisting of an acrylonitrile; a N-alkoxyalkyl acrylamide; a vinylacetate; a vinylformamide; a vinyl acetamide; a vinyl methyl ether; avinyl pyrrolidone; an acrylate; a vinyl siloxane; and any combinationthereof.

Element 5: Wherein the polar monomer is capable of generating acarboxylate group.

Element 6: Wherein the ionizable polar monomer is selected from thegroup consisting of a carboxylic acid; a carboxylic acid derivative; asalt of carboxylic acid; a sulfonic acid; a salt of sulfonic acid; andany combination thereof.

Element 7: Wherein the crosslinked water swellable superabsorbentpolymer is selected from the group consisting of a crosslinkedpolyacrylate-based polymer; a crosslinked polyacrylamide-based polymer;a crosslinked polyvinyl alcohol polymer; a crosslinkedstarch-polyacrylonitrile graft polymer; any copolymer thereof; anyterpolymer thereof; and any combination thereof.

Element 8: Wherein the hydrophobically modified water-soluble polymer isformed by hydrophobic modification of a hydrophilic polymer.

Element 9: Wherein the hydrophobically modified water-soluble polymer isformed by a polymerization reaction of a hydrophilic monomer and ahydrophobically modified hydrophilic monomer.

Element 10: Wherein the vulcanized oil and water swellable particulatecomposite further comprises a polyvalent metal oxide; a reinforcingmaterial; and any combination thereof.

By way of non-limiting example, exemplary combinations applicable to Aand B include: A with 1, 3, and 5; A with 2 and 10; B with 4, 7, and 8;and B with 6 and 9.

To facilitate a better understanding of the embodiments describedherein, the following examples of preferred or representativeembodiments are given. In no way should the following examples be readto limit, or to define, the scope of the disclosure.

EXAMPLE

A vulcanized oil and water swellable particulate composite was preparedaccording to some embodiments described herein using first melt blending(mastication) followed by molding. The vulcanized oil and waterswellable particulate composites were melt blended using a rubber mixersupplied by Brabender. The three platens of the rubber mixer werepre-heated at 70° C. (158° F.) and the screw rotation rate was set at 30RPM. The rubber mixer was loaded in the following order: elastomer,hydrophobically modified water-soluble polymer, swellable superabsorbentpolymer (the swellable superabsorbent polymer was premixed prior to meltblending), reinforcing agent, and vulcanizing agent, each describedbelow. The mixture was blended in the rubber mixer for 30 minutes at 30RPM. The mixture was removed and cut into small pieces for molding intocubic prisms. To mold the mixture into cubic prisms, about 6 grams ofthe mixture was loaded into a 2.54 cm×2.54 cm×0.64 cm (1 in×1 in×0.25in) metal mold and vulcanized (cured) and compression molded at 177° C.(350.6° F.) for 20 minutes under a load of about 2000 to 3000 pounds.

In this example, the ability of the vulcanized oil and water swellableparticulate composites made according to the process described above toswell in the presence of an aqueous fluid were evaluated: (1) when theelastomer in the vulcanized oil and water swellable particulatecomposite is a crosslinked carboxylated butadiene acrylonitrile(“XNBR”), as described in the embodiments herein, as compared to anon-carboxylated butadiene acrylonitrile (“NBR”) (i.e., without theionizable polar monomer) (Control Composition 1 (“CC1”)), (2) when thevulcanized oil and water swellable particulate composites comprise ahydrophobically modified water-soluble polymer (e.g., NATROSOL® PLUS CS,Grade 330; PEMULEN™ TR-1; and PEMULEN™ TR-2, as described herein), ascompared to a non-hydrophobically modified water soluble hydroxyethylcellulose polymer (or Free Water Control Agent, “FWCA”) (ControlComposition 2 (“CC2”)), (3) when the amount and type of hydrophobicallymodified water-soluble polymer is varied, and (4) when the vulcanizedoil and water swellable particulate composite further comprises thepolyvalent metal oxide, magnesium oxide. The Test Composites are labeledTC1 through TC5. The compositions of the composites are included inTABLE 1, and are described in parts per hundred rubber with reference tothe elastomer (“PHR”).

TABLE 1 Component CC1 CC2 TC1 TC2 TC3 TC4 TC5 ELASTOMER XNBR 100 100 100100 100 100 NBR 100 WATER-SOLUBLE POLYMER FWCA 10 (non-hyrophobicallymodified water- soluble hydroxyethyl cellulose polymer) NATROSOL ® PLUSCS, Grade 330 10 20 (hydrophobically modified hydroxyethyl cellulose)PEMULEN ™ TR-1 10 10 (hydrophobically modified polyacrylic acid with lowlevel of hydrophobic groups) PEMULEN ™ TR-2 10 10 (hydrophobicallymodified polyacrylic acid with high level of hydrophobic groups)SUPERABSORBENT POLYMER HYSORB ™ 8100 100 100 100 100 100 100 100VULCANIZING AGENT VUL-CUP 40KE 2 2 2 2 2 2 2 REINFORCING AGENT CarbonBlack 30 30 30 30 30 30 30 POLYVALENT METAL OXIDE Magnesium Oxide 1WATER Fresh Water 30 30 30 30 30 30 30

Molded prisms of 2.54 cm×2.54 cm×0.635 cm (1 in×1 in×0.25 in) of each ofCC1, CC2, or TC1-TC5 were submerged separately in both 150 mL of freshwater and a 150 mL of a 1% NaCl solution for 7 days at 22.22° C. (72°F.) and tested for hardness using a Shore A durometer and observed forswelling behavior. The Shore A hardness results are listed in TABLE 2.

The Shore A hardness values are largely similar. However, theswellability observations demonstrate the superiority of the vulcanizedoil and water swellable particulate composites as described herein.First, ionic polar groups (carboxylate groups in this example) improveelastomer performance, as compared to elastomers lacking such groups.Such improved performance is likely due to improved compatibilitybetween the elastomer, the crosslinked water swellable superabsorbentpolymers, and the hydrophobically modified water-soluble polymer.

TABLE 2 CC1 CC2 TC1 TC2 TC3 TC4 TC5 Shore A Hardness 90 93 90 92 91 9393

Comparing the swellability observations of CC1 to TC1, CC1 is identicalto TC1, except that TC1 comprises a carboxylated elastomer, having anionizable polar monomer. CC1 released more reinforcing agent into thefresh water that it was submerged in, suggesting that the ionizablepolar groups improve elastomer performance.

CC2 lacked a hydrophobically modified water-soluble polymer, comprisinginstead a non-hydrophobically modified water-soluble polymer. Theparticulate composite released swollen gel blobs, released carbon blackinto the fresh water that it was submerged in, and the fresh water wasviscous, demonstrating that either the non-hydrophobically modifiedwater-soluble polymer in the particulate composite was not able toadequately retain the crosslinked water-swellable superabsorbent polymeror preferred to leach into the aqueous fluid. Comparing CC2 to TC1through TC5, each one having a hydrophobically modified water-solublepolymer in accordance with the embodiments described herein, TC1 throughTC5 exhibited less or no released swollen gel blobs and less or noincrease in viscosity in the fresh water.

Comparing TC2 and TC3, each identical except that TC3 comprised anincreased amount of NATROSOL® PLUS CS, Grade 330 (hydrophobicallymodified hydroxyethyl cellulose), both demonstrated less swollen gelblobs in comparison to CC2, which lacked a hydrophobically modifiedwater-soluble polymer, less release of carbon black into the freshwater, and less or no increase in viscosity of the fresh water. Thisindicates that the presence of a hydrophobically modified water-solublepolymer in the vulcanized oil and water swellable particulate compositesdescribed herein improves swelling behavior and increased resistance toseparation of the various components of the particulate composite.

Comparing TC1 and TC4, the increased hydrophobic groups present in thehydrophobically modified water-soluble polymer in TC4 compared to TC1improved the swelling behavior and reduced the release of carbon black,demonstrating that higher levels of hydrophobic groups may be preferred.

Comparing TC4 and TC5, each identical except that TC5 additionallycomprises a polyvalent metal oxide, magnesium oxide, TC5 demonstratedimproved swellability and reduced carbon black release.

Molded prisms of 2.54 cm×2.54 cm×0.635 cm (1 in×1 in×0.25 in) of each ofCC2 and TC1-TC5 were submerged separately in 150 mL of fresh water at22.2° C. (72° F.) for 7 days and evaluated for weight gain (i.e.,swellability rates) at various time periods between day 1 through day 7.FIG. 2 shows a graphical depiction of the results. Molded prisms of 2.54cm×2.54 cm×0.635 cm (1 in×1 in×0.25 in) of each of TC1-TC5 weresubmerged separately in 150 mL of a 1% NaCl solution at 22.2° C. (72°F.) for 7 days and evaluated for weight gain (i.e., swellability rates)at various time periods between day 1 through day 7. FIG. 3 shows agraphical depiction of the results. FIG. 2 and FIG. 3 show a graphicaldepiction of the swellability observations discussed above and indicatethat very high swell rates can be obtained using the vulcanized oil andwater swellable particulate composites disclosed herein, both at lowtemperatures and in the presence of a salt solution. Indeed, thevulcanized oil and water swellable particulate composites of theembodiments herein are capable of absorbing water in the range of about20% to about 400% by weight in dry form.

Therefore, the embodiments disclosed herein are well adapted to attainthe ends and advantages mentioned as well as those that are inherenttherein. The particular embodiments disclosed above are illustrativeonly, as they may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularillustrative embodiments disclosed above may be altered, combined, ormodified and all such variations are considered within the scope andspirit of the disclosure. The embodiments illustratively disclosedherein suitably may be practiced in the absence of any element that isnot specifically disclosed herein and/or any optional element disclosedherein. While compositions and methods are described in terms of“comprising,” “containing,” or “including” various components or steps,the compositions and methods can also “consist essentially of” or“consist of” the various components and steps. All numbers and rangesdisclosed above may vary by some amount. Whenever a numerical range witha lower limit and an upper limit is disclosed, any number and anyincluded range falling within the range is specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues. Also, the terms in the claims have their plain, ordinary meaningunless otherwise explicitly and clearly defined by the patentee.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces. If there is any conflict in the usages of a word or term inthis specification and one or more patent or other documents that may beincorporated herein by reference, the definitions that are consistentwith this specification should be adopted.

The invention claimed is:
 1. A vulcanized oil and water swellableparticulate composite comprising: an elastomer, a crosslinked waterswellable superabsorbent polymer, and a hydrophobically modifiedwater-soluble polymer, wherein the elastomer comprises a non-polarmonomer, a polar monomer, and an ionizable polar monomer, and whereinthe vulcanized oil and water swellable particulate composite is capableof swelling in the presence of a non-aqueous fluid and an aqueous fluid.2. The composite of claim 1, wherein the non-polar monomer is selectedfrom the group consisting of a diene; a substituted diene; analpha-olefin; and any combination thereof.
 3. The composite of claim 1,wherein the polar monomer is non-ionic.
 4. The composite of claim 1,wherein the polar monomer is selected from the group consisting of anacrylonitrile; a N-alkoxyalkyl acrylamide; a vinyl acetate; avinylformamide; a vinyl acetamide; a vinyl methyl ether; a vinylpyrrolidone; an acrylate; a vinyl siloxane; and any combination thereof.5. The composite of claim 1, wherein the polar monomer is capable ofgenerating a carboxylate group.
 6. The composite of claim 1, wherein theionizable polar monomer is selected from the group consisting of acarboxylic acid; a carboxylic acid derivative; a salt of carboxylicacid; a sulfonic acid; a salt of sulfonic acid; and any combinationthereof.
 7. The composite of claim 1, wherein the hydrophobicallymodified water-soluble polymer is formed by hydrophobic modification ofa hydrophilic polymer.
 8. The composite of claim 1, wherein thehydrophobically modified water-soluble polymer is formed by apolymerization reaction of a hydrophilic monomer and a hydrophobicallymodified hydrophilic monomer.
 9. The composite of claim 1, wherein thevulcanized oil and water swellable particulate composite furthercomprises a polyvalent metal oxide; a reinforcing material; and anycombination thereof.
 10. A vulcanized oil and water swellableparticulate composite comprising: an elastomer, a crosslinked waterswellable superabsorbent polymer, and a hydrophobically modifiedwater-soluble polymer, wherein the elastomer comprises a non-polarmonomer, a polar monomer, and an ionizable polar monomer, wherein thevulcanized oil and water swellable particulate composite is capable ofswelling in the presence of a non-aqueous fluid and an aqueous fluid,and wherein the crosslinked water swellable superabsorbent polymer isselected from the group consisting of a crosslinked polyacrylate-basedpolymer; a crosslinked polyacrylamide- based polymer; a crosslinkedpolyvinyl alcohol polymer; a crosslinked starch-polyacrylonitrile graftpolymer; any copolymer thereof; any terpolymer thereof; and anycombination thereof.
 11. The composite of claim 10, wherein thenon-polar monomer is selected from the group consisting of a diene; asubstituted diene; an alpha-olefin; and any combination thereof.
 12. Thecomposite of claim 10, wherein the polar monomer is non-ionic.
 13. Thecomposite of claim 10, wherein the polar monomer is selected from thegroup consisting of an acrylonitrile; a N-alkoxyalkyl acrylamide; avinyl acetate; a vinylformamide; a vinyl acetamide; a vinyl methylether; a vinyl pyrrolidone; an acrylate; a vinyl siloxane; and anycombination thereof.
 14. The composite of claim 10, wherein the polarmonomer is capable of generating a carboxylate group.
 15. The compositeof claim 10, wherein the ionizable polar monomer is selected from thegroup consisting of a carboxylic acid; a carboxylic acid derivative; asalt of carboxylic acid; a sulfonic acid; a salt of sulfonic acid; andany combination thereof.
 16. The composite of claim 10, wherein thehydrophobically modified water-soluble polymer is formed by hydrophobicmodification of a hydrophilic polymer.
 17. The composite of claim 10,wherein the hydrophobically modified water-soluble polymer is formed bya polymerization reaction of a hydrophilic monomer and a hydrophobicallymodified hydrophilic monomer.
 18. The composite of claim 10, wherein thevulcanized oil and water swellable particulate composite furthercomprises a polyvalent metal oxide; a reinforcing material; and anycombination thereof.